The invention relates to a battery including rechargeable cells in series.
A field of application of the invention is in power batteries, such as for example those used as an energy source for driving a traction motor drive in electric vehicles. This type of onboard battery of an electric vehicle for example has cells of lithium-metal-polymer technology. Of course, the battery may have other applications, for example for powering fixed devices. The cells of the battery may be loaded by connecting the latter to a suitable charger.
The power consuming device, powered by the battery, may if necessary recharge the cells, such as for example in the case of an electric vehicle in a braking situation, in which a regeneration electric current is provided from the traction motor drive to the battery. The use of the battery by a power-consuming device imposes control of the regeneration and discharge phases.
Indeed, upon operating the battery, overload or excessive regeneration cause oxidation of the products making up the positive electrode and the electrolyte of the battery. This oxidation causes alteration of the battery, which means notably a rapid increase in the internal resistance. Intensive and prolonged overloading may have the consequence of destruction of the battery.
Excessive discharge causes a parasitic electrochemical reaction within the active material of the positive electrode, with the consequence of rapid and irreparable lowering of the capacity of the battery. This reaction also has the consequence of an increase in the internal resistance. Thus, excessive regeneration and/or excessive discharge substantially reduce the lifetime of the battery.
Further, regeneration of the battery at a too low temperature substantially promotes the formation of dendrites, which also causes a reduction in the lifetime of the battery. A discharge at a too low temperature will have the consequence of faster lowering of the voltage because of the high internal resistance of the battery.
The invention is directed to obtaining a battery with which it is possible to prevent excessive discharges and/or excessive regenerations during its use by a power-consuming device, in order to preserve the lifetime of the battery. For this purpose, a first object of the invention is a battery including a pack of a plurality of modules, each containing a multiplicity of rechargeable cells in series, the battery further including means for measuring the voltage of at least one cell and/or the temperature of at least one module,                characterized in that it includes:        means for computing, based on the voltage and/or temperature measured by the measuring means and on a recorded characteristic of the discharge current and/or regeneration current of the battery, a maximum discharge and/or regeneration current limit of the pack,        a transmission means for transmitting outside the information on the maximum discharge and/or regeneration current limit of the pack.        
In an embodiment of the invention, the modules are in series and the recorded current characteristics from the computing means relate to the modules in series.
In an embodiment of the invention,                the battery includes:                    on each module, means for measuring the voltage of several cells of the module, and/or            means for measuring the temperature of several modules, and                        the computing means include:                    first means for computing, from the voltages and/or temperatures measured by the measuring means, at least one first extremal quantity, selected from:                            a first maximum cell voltage,                a second maximum module voltage,                a third minimum cell voltage,                a fourth minimum module voltage,                a fifth maximum module temperature,                                    second means for computing, as a maximum discharge and/or regeneration current limit of the pack, at least one value from:                        a maximum authorized pack regeneration current value depending on the first and/or second maximum voltage,        a maximum authorized pack discharge current value depending on the third and/or fourth minimum voltage,        a maximum admissible pack regeneration current value depending on the fifth maximum module temperature,        a maximum admissible pack discharge current value depending on the fifth maximum module temperature.        
According to other features of the invention:                Each module includes the first computing means, one of the modules is a master, while the other modules are slaves of the master module so as to transmit to it said at least one first extremal quantity through a communications network connecting the modules with each other, the second computing means and the outward transmission means being provided on the master module.        The maximum authorized regeneration current value is computed by the second means, so that:        it is equal to a first upper regeneration current value when the second maximum module voltage is less than a first module voltage threshold,        it is equal to a second intermediate regeneration current value when both the second maximum module voltage is larger than or equal to the first module voltage threshold and the first maximum cell voltage is less than a first cell voltage threshold,        it is equal to a third lower regeneration current value, when both the first maximum cell voltage is larger than or equal to the first cell voltage threshold and less than a second cell voltage threshold, and the second maximum module voltage is less than a second module voltage threshold,        it is zero, when the first maximum cell voltage is larger than or equal to the second cell voltage threshold or when the second maximum module voltage is larger than or equal to the second module voltage threshold,        the first cell voltage threshold being smaller than the second cell voltage threshold, and the first module voltage threshold being smaller than the second module voltage threshold;        The maximum authorized discharge current value is computed by the second means so that:        it is equal to a first intermediate discharge current value, when both the fourth minimum module voltage is larger than or equal to a third module voltage threshold and less than a fourth module voltage threshold, and the third minimum cell voltage is larger than or equal to a third cell voltage threshold and less than a fourth cell voltage threshold,        it is equal to a second upper discharge current value when both the third minimum cell voltage is larger than the fourth cell voltage threshold and the fourth minimum module voltage is larger than the fourth module voltage threshold,        it is zero otherwise;        The maximum admissible regeneration current value is calculated by the second means, so that        it is equal to a fourth upper regeneration current value, when the fifth maximum module temperature is less than a first module temperature threshold,        it is equal to a decreasing function of the fifth maximum module temperature, when the fifth maximum module temperature is larger than or equal to the first module temperature threshold and less than a second module temperature threshold, the values of this function being less than or equal to the fourth upper regeneration current value and larger than or equal to a fifth lower regeneration current value,        it is otherwise equal to the fifth lower regeneration current value, either positive or zero;        The maximum admissible discharge current value is computed by the second means, so that        it is equal to a first upper discharge current value, when the second maximum module temperature is less than a first module temperature threshold,        it is equal to a decreasing function of the fifth maximum module temperature, when the fifth maximum module temperature is larger than or equal to the first module temperature threshold and less than a second module temperature threshold, the values of this function being less than or equal to the fourth upper discharge current value and larger than or equal to a fifth lower discharge current value,        it is otherwise equal to the fifth lower discharge current value, either positive or zero;        The decreasing function of the fifth maximum module temperature is linear;        The second means are provided for computing, for the discharge current and/or the regeneration current, both a maximum authorized value and a maximum admissible value,        the maximum discharge and/or regeneration current limit of the pack being the largest of both the maximum authorized value and the maximum admissible value;        The battery includes means for measuring the voltage of each cell and/or means for measuring the temperature of each module;        The battery includes means for measuring the module temperature in at least two different zones of the module, the measured temperature of the module being the largest of the temperatures of the zones of the module;        The transmission means comprises an interface with a network for communication to the outside;        The cells are made by assemblies of thin films;        The cells have a nominal operating temperature above 20° C.;        The cells are of the lithium-metal-polymer type;        Each module further includes at least one unit for heating its cells to their nominal operating temperature above 20° C.        
A second subject matter of the invention is a motor vehicle, including a traction motor drive and at least one battery as described above, for supplying at least temporarily the traction motor drive with electric power, characterized in that the traction motor drive includes a supervisor having means for receiving information on the maximum discharge and/or regeneration current limit of the pack, sent by the transmission means of the battery.